Why not 3D print something for it? I printed this to make a digital photo frame with a Pi 4 and the official 7" Pi touch display. https://www.printables.com/model/44218-7-touchscreen-case-for-raspberry-pi-4-internal-fan

Printing it with something strong should help keep it safe in an accident though you’ll need to create a mounting solution.

I went through the exact same situation with my 20 year old music collection and MusicBrainz Picard and unfortunately this is just the state of music piracy even now as things are rarely tagged correctly or come from compilation albums, sample albums, or are just obscure and don’t have the proper tags available on the service. This is why I don’t mind paying for music streaming even though I selfhost most other media formats because you can put in days of work tagging songs and still have a jumbled mess at the end (Picard’s tagging template is also a huge PITA to use with some obscure legacy language).

I think the Define 5 is a good option as well. I bought the 6 in 2018 because it was new, was white, and only like $99 at the time and it’s served me well. Every couple of years I’d buy some more drive trays as my pool filled up and I needed more space.

I just rebuilt my whole system a couple of months ago but kept the case because it works so well and there isn’t much on the market like it without getting into fullsize cases. It’s nearly silent even with 5 fans and 9 HDDs inside. It sits about 2 feet from me on my desk and I only hear a tiny hum from the fans.

PC Part Picker has filters that will let you set all your requirements and show you what’s available. Since you want ECC and low cost, you might be better off finding options on PCPartPicker and then looking for those items used on ebay.

If you don’t have a case already, you might check out Fractal Design. They have several cases for lots of 3.5" drives. I have a Define 6 and it holds like 12 3.5" and 4 2.5" in a midtower format and it’s constructed really well. You will need to buy additional drive trays though as they only come with 4 I think.

How big are these ZFS snapshots compared to the stored data size? 1:1?

I would hope one would use an SSD for something like HomeAssistant. HDDs really shine as bulk media storage (music, pictures, video) not as storage for what would be the equivalent of running an OS on it.

It’s “powerful” in the sense that it has 48 PCI lanes and can use almost 800GB of memory (ECC included). This is just way overkill on most homelabs so the extra power draw isn’t worth it.